The conventional way of forming butt joints between aligned profiles of this nature is to provide a strap with opposite extremities extending into the two channels thereof, these strap extremities and the channel bottoms being formed with aligned apertures to be traversed by fasteners such as bolts or rivets. A drawback of that arrangement is the need for perforating the channel bottom, which requires a separate operation, and for exactly locating these apertures in order to avoid the existence of an unsightly gap between the adjoining channel ends. The elimination of such a gap is also necessary where leakage of a liquid carried by the channel is to be prevented.